Determining angles and directions is required in many fields of application such as geodesy, building construction and civil engineering, industrial automation technology, etc. In this case, high demands are placed on the measuring precision, the measuring speed, and the degree of availability; and all of this is also under rough environmental conditions.
JP 57100304 discloses an angle measuring device, which uses a spot-shaped object light beam and, as an alternative to an optical lens which is susceptible to dirt and damage, a two-dimensional hologram. For this purpose, the hologram is inscribed in a flat plate. Accordingly, the degree of transmission is only dependent on two spatial directions. The corresponding dependence of the location in a plane of the real image of the object light beam hologram on the angle of incidence of the light beam is used. The location of the spot image changes continuously in the event of a corresponding angle of incidence change. It is acquired using a position sensor and the respective angle of incidence is inferred therefrom. DE 3424806 A1 describes a measuring unit for the contactless acquisition of a relative position between a first element and a second element, which, in contrast to JP 57100304, ascertains angles via the readout of a code. Such an element can be a component of a precision machine, and it can also be a device scale of an optical instrument.
The two elements are spatially separated from one another over a distance of 100 m, for example. The first element has a code carrier, and the second element has a code reader having a computer downstream from the code reader. The code reader acquires a one-dimensional code pattern of the code carrier and transmits a code signal to the computer for an acquired code pattern. The computer has means for quantification of the transmitted code signal and for comparison to a stored code pattern and for calculation of the relative position between the first element and the second element from the result of the comparison.